A relatively simple adaptation to a bird table to make an upstand can give you the opportunity to plant the roof. You need a water retaining mat and an ‘off cut’ of Sedum roof ‘turf’… (if you can get it! ) otherwise you can just plant the Sedum yourself! Children can help you do this, measuring the timber edges, learning to use a saw, screwdriver etc. as well as doing the planting. Happy birds.